Derivatives of epsilon-caprolactam



Jan. 14, 1969 H. K. REIMSCHUESSEL ETAL 3,

I DERIVATIVES OF EPSILON-CAPROLACTAM I Filed Sept. 13, 1955 a WAVELENGTH (MICRONS) III 999 00- INVENTORS: HDNVGEOSQV HERBERT K.REIMSCHUESSEL JOHN V. PASCALE TTORNEY United States Patent 3,422,093 DERIVATIVES 0F EPSILON-CAPROLACTAM Herbert K. Reimschuessel, Morristown, and John V. Pascale, Parsippany, N..l-, assignors to Allied Chemical Corporation, New York, N.Y., a corporation of New York Filed Sept. 13, 1965, Ser. No. 486,636 US. 'Cl. 260-239.3 Int. Cl. C07d 41 /06'; C08g 20/12 9 Claims ABSTRACT OF THE DISCLOSURE Although epsilon-caprolactam is readily polymerized to form polymers generally known as nylon 6, derivatives of epsilon-caprolactam, wherein one of the hydrogen atoms attached to a carbon atom of the heterocyclic sevenmembered ring is replaced by an organic radical, are generally extremely difficult, if not impossible, to polymerize. As an exception to this rule, there is disclosed in copending application Ser. No. 341,068 filed Jan. 29, 1964 a class of readily polymerizable epsilon-caprolactam derivatives having alpha-substituents containing at least one meta-directing elctrophilic group. An example of such a monomer is alpha-(carboxymethyl)caprolactam which forms a highly crosslinked polymer which is amorphous, infusible, and insoluble in most solvents.

We have now discovered that high molecular weight linear polymers can be prepared from beta-(carboxymethyl)caprolactam. These polymers are highly crystalline as obtained or are readily convertible to the crystalline state.

In accordance with the present invention, beta-(carboxymethyl)caprolactam is polymerized at a temperature ranging from the melting pointof the monomer (191- 193 C.) up to about 350 C. with the reaction preferably being conducted in an inert atmosphere such as nitrogen. When polymerized, the monomer rearranges to form a material composed of recurring units containing a glutarimide ring structure as illustrated in the following equation:

P O CHr C "ice amorphous polymer which can readily be converted to the crystalline state by annealing in a dry inert atmosphere or in steam at a temperature of C. or above. The molecular weight of the polymer can be controlled by the addition of so-called viscosity regulators to the monomer prior to polymerization. This eifect is illustrated in Example 4 wherein the viscosities of polymer samples are progressively lowered by the addition of increasing quantities of the n-butyl ammonium salt of beta-(carboxymethyl)caprolactam. The addition of amines, or anhydrides of carboxylic acids, have a similar elfect upon the molecular weight. It has also been found that admixing water with the monomer prior to polymerization also tends to lower the viscosity of the polymer obtained.

Employing the polymerization procedure of this invention, conversions of monomer to polymer of over 95% have been obtained. The polymer has a crystalline melting point of about 275 C. and a density of about 1.3 grams/cm The polymer is further characterized by high thermal stability and a good stability against hydrolytic degradation. The thermal decomposition temperature of the polymer was found to be about 50 C. higher than those of both nylon and polyethylene terephthalate when tested under identical conditions. For instance, when heated in a differential thermal analysis apparatus at a rate of heating of 20 C. /min., the polymer of this invention decomposed at 458 C. while nylon 6 decomposed at 410 C. and polyethylene terephthalate at 409 C. Stability against hydrolytic degradation was tested by heating polymeric samples in saturated steam at 170 C. lbs/sq. in.); 190C. (18 2lbs./sq. in); and 205 C. (250 lbs/sq. in.) for 15 minutes. Nylon 6 dissolved at C. and nylon 66 at C. while the polymer of this invention withstood the above conditions at 205 C. The polymer produced from beta-(carboxymethyl) caprolactam can be formed into tough films and fibers which can be drawn. This drawing, accomplished at a temperature of at least 100 C., i saccompanied by some crystallization, and it is generally preferred to eifect further crystallization of the product by annealing. The polymer is soluble in meta-cresol, sulfuric acid, and formic acid, and can be cast into films from solutions in these sol-vents. In the accompanying figure, there is shown a typical infrared spectrum of the polymer of this invention with optical density plotted against wave length in microns.

The beta-(carboxymethyl)caprolactam used as a monomer in the present invention is itself a novel compound and it is prepared by a process involving a number of novel intermediates. The process which we have employed starts with a known compound alpha, beta-unsaturated caprolactam and then proceeds through a series of novel steps. In the first step, the alpha, beta-unsaturated caprolactam is reacted with a sodium dialkyl malonate (reaction product of metallic sodium with a dialkyl malonate) to form a beta-(dicarbalkoxymethyl)caprolactam in accordance with the following equation:

wherein R is a lower alkyl group preferably containing one to five carbon atoms. This process can be readily carried out by adding the alpha, beta-unsaturated caprolactam to an alcoholic solution of sodium dialkyl malonate and refluxing the resulting reaction mixture.

The beta-(dicarbalkoxymethyl)caprolactam is next wherein R has the meaning given above and X is an alkali metal. The monomer beta-(carboxymethyl)caprolactam is prepared by decarboxylation of beta-(dicarbalkoxymethyl) caprolactam at elevated temperatures. This is preferably carried out by heating the beta-(dicarbalkoxymethyl)caprolactam at a temperature of about l40190 C. in a solvent medium such as o-dichlorobenzene until the evolution of carbon dioxide ceases. The beta-(carboxyniethyl)caprolactam is then recovered and polymerized by heating it at a temperature of 191 to 350 C. as previously described.

As an alternative procedure, the polymer can be produced from the beta- (dicarbalkoxymethyl)caprolactam without isolating the beta(carboxymethyl)caprolactam monomer. For instance, the beta-(dicarbalkoxymethyl) caprolactam can be subjected to a heat treatment, including temperatures of over 191 C., thus, not only driving off the carbon dioxide but also forming a polymer. However, although such a procedure is more direct, it is less difficult to obtain a pure, high molecular weight polymer when the beta-(carboxymethyl)caprolactam is separated from the reaction mixture prior to the preparation of the polymer.

It is also to be noted that poly[beta(n-propyl)glutarimide] can be produced from derivatives of beta(carboxymethyl)caprolactams which are readily hydrolizable back to beta-(carboxymethyl)caprolactam. For instance, polymer can be produced from esters of beta(carboxymethyl)caprolactam such as the lower alkyl esters. These compounds can be prepared by the esterification of beta- (carboxymethyl)caprolactam with the appropriate alcohol. Beta-(carbalkoxymethyl)caprolactam esters can also be made from the previously disclosed beta(dicarbalkoxymethyl)caprolactam by reacting this latter compound with only one equivalent of alkali metal hydroxide to thereby convert only one carboxy group per molecule to a salt radical, acidifying the resulting compound to form a monoacid, and then heating the monoacid to drive off carbon dioxide. These reactions are illustrated by the following equation:

wherein R and X have the meanings given above.

In addition to being useful in the preparation of poly [beta(n-propyl)glutarimide], the monomers of this invention can be polymerized with other monomers. For instance, a particularly outstanding copolymer can be prepared by copolymerizing the present monomers with epsilon-caprolactam.

The following examples are given to further illustrate the invention, but it is to be understood that the invention is not to be limited in any way by the details described therein. In the examples, reduced viscosities were measured in meta-cresol at concentrations of 0.5 gram of polymer per milliliters of solution, the units accordingly being deciliters per gram.

EXAMPLE 1 384 grams of alpha-bromocaprolactam and 400 ml. of 2,6-lutidine were heated to reflux with stirring for 3 hours. Upon cooling, the solution was filtered and 376 grams of 2,6-lutidine hydrobromide were collected. The filtrate obtained contained alpha,beta-unsaturated caprolactam and was dried with anhydrous sodium sulfate. The solution was reduced under vacuum to 800 ml. and then added to an alcoholic solution of sodium diethyl malonate. The latter solution had been prepared by adding 50.6 grams of sodium to 3 liters of anhydrous ethanol, followed by the addition of 640 grams of diethyl malonate to the refluxing solution, and continued heating at reflux for 3 hours. The resulting reaction mixture was then heated to reflux for an additional 5 hours, filtered, and distilled to remove both the benzene and ethanol. The remaining solution was diluted with ethyl ether. The ether solution was then washed with 10% hydrochloric acid, saturated sodium bicarbonate solution, and finally with water. After removal of both the ether and the excess diethyl malonate under vacuum, the remaining viscous oil was extracted with petroleum ether and the resulting solid material recrystallized from hexane. There were obtained 352 grams of beta-(dicarbethoxymethyl)caprolactam that melted at 4950 C.

Analysis.-Calculated for C H O N: C, 57.55%; H, 7.80%; N, 5.16%. Found: C, 57.18%; H, 7.59%; N 5.42%.

EXAMPLE 2 A solution of 352 grams of beta-(dicarbethoxymethyl) caprolactam in 500 ml. of absolute ethanol was added with stirring to a solution of 175 grams of potassium hydroxide in one liter of anhydrous ethanol. The resulting mixture was heated to reflux for 6 hours. After cooling to room temperature, the formed dipotassium salt was collected by filtration, washed with ethanol, and dried. 370 grams of this salt were obtained. This material was then dissolved in 250 ml. of water and the solution was cooled to minus 5 plus C. The cooled solution was then acidified with 241 ml. of concentrated hydrochloric acid. The resulting precipitate was collectedand recrystallized' from methanol. 280 grams of material composed of beta-(dicarboxymethyl)caprolactam and some potassium chloride were obtained. 40-gram portions of this material were added to one liter of o-dichlorobenzene which had been heated to 160-170 C. After the evolution of carbon dioxide had ceased, the resulting solutions were filtered. Upon cooling, 174 grams of .beta-(carboxyme thyl)caprolactam were obtained. Recrystallization from water yielded a white crystalline product that melted at"'l9l193 C.

Analysis.-Calculated for C H O N: C, 56.13%;H, 7.65%; N, 8.18%. Found: C, 56.12%; H, 7.36%; N, 8.91%.

EXAMPLE 3 Ten grams of beta-(carboxymethyl)caprolactam and 2 ml. of water were placed into a polymerization tube maintaining a nitrogen atmosphere. The tube was then immersed into a Woods metal bath which had been heated to 240 C. After 1 /2 hours, the contents of the tube had been solidified. At this point, it was removed from the polymerization tube, ground, and analyzed. The polymer was identified as poly[beta(n-propyl)glutarimide]. Extraction with hot water indicated that 95% of the material had polymerized. The polymer was found to be soluble in meta-cresol, formic acid, and sulfuric acid; it was insoluble in the common organic solvents. The reduced viscosity as measured in meta-cresol was 0.54. The polymer melted .at 275 C., decomposed at 450 C., and had a density of 1.3 tgm./cm. The infrared absorption spectrum of the polymer is shown in the figur Ten grams of beta-(oarboxymethyl)caprolactam and one milliliter of water were then heated at 240 C. for 3 hours as described above. The resulting polymer had a reduced viscosity of 0.78 and a melting point of 275 C.

Ten grams of beta-(carboxymethyl)caprolactam were next heated at 290 C. for 20 hours as described above without the addition of water. The resulting polymer had a reduced viscosity of 5.3 and a melting point of 275 C.

EXAMPLE 4 TABLE I Mole ratio beta-(carboxymethyl)caprolactam: salt Reduced viscosity in meta-cresol 50:1 0.73 100:1 1.11 200:1 1.69 500:1 2.91 No salt 4.49

The polymers were amorphous, but they could be readily crystallized by annealing at a temperature of at least 100 C.

EXAMPLE 5 Ten grams of beta-(dicarboxymethyl)caprolactam were heated under nitrogen to 200 C. for one hour. The

temperature was then raised to 290 C. and held there for 4 hours. The resulting polymer had a reduced viscosity in meta-cresol of 0.7. The polymer had a melting point of 270-280 C. and was identified as poly[beta(n-propyl) glutarimide] EXAMPLE 6 Into a polymerization tube that was heated to 200 C. were placed under nitrogen 4 parts of beta-(carboxymethyDcaprQlactam and 2.64 parts of epsilon-caprolactam. The temperature was then raised to 260 C. and held there for 20 hours. A clear polymer was obtained having a viscosity of 0.5 in meta-cresol.

EXAMPLE 7 In a mixture containing ml. of ethanol, 20 ml. of benzene and 2 ml. of concentrated sulfuric acid, 34.24 grams of beta-(carboxymethyl)caprolactam were dissolved. This solution was refluxed for 4 hours. The excess solvent was then removed by distillation and the residue dissolved in ether. The ether solution was washed with saturated sodium bicarbonate solution .and dried over anhydrous sodium sulfate. The ether was removed in vacuum and the residue recrystallized from n-hexane. There were obtained 27.3 grams of beta-carbethoxymethyl)caprolacta.-m having a melting point of 78 C.

Analysis.-Calculated for C OH O N'z C, 60.28%; H, 8.60%; N, 7.03%. Found: C, 59.94%; H, 8.62%; -N, 6.94%.

Ten grams of the beta-(carbethoxymethyl)caprolactam were placed into a polymerization tube while maintaining a nitrogen atmosphere. The tube was heated at 290 C. for 20 hours, thereby producing poly [beta(n-propyl) glutarimide] having a reduced viscosity of 0.59.

EXAMPLE 8 To a solution containing 27.13 grams of beta-(dicarbethoxymethyl)caprolactam in 75 ml. of anhydrous ethanol solution is added 5.6 grams of potassium hydroxide dissolved in 60 ml. of anhydrous ethanol. The resulting solution is held at room temperature until the pH of this solution is 7. At this point, the solution is heated under reflux for one hour, filtered, and the ethanol distilled under vacuum. To the residue is added ethyl ether. The salt which forms is removed by filtration, washed with ether, and dried under vacuum. Thesalt is dissolved in ml. of chloroform and the solution cooled below 0 C. An equivalent amount of hydrochloric acid is added and the chloroform distilled under reduced pressure. The residue is beta-(carboxy-carbethoxymethyl)- caprolactam. material is decarboxylated by heating at C. to yield beta-(carbethoxymethyl)caprolactam, melting point- 7879.5 C. Heating lita-(carbethoxymethyl)caprolactam at 290 C. in a nitrogen atmosphere gives poly [betaIn-propyl)glutarimide].

EXAMPLE 9 Molded films were prepared from poly[beta(n-propyl)- glutarimide] having reduced viscosities of 3.0 and 1.6, and the tensile properties of these films were determined in accordance with ASTM Test D882. The results are shown in the following table:

It will be apparent that many modifications and variations may be effected without departing from the scope of the novel concepts of the present invention and the illustrative details disclosed are not to be construed as imposing undue limitations on the invention.

7 We claim: 1. A compound of the formula 0 I ll t C CH2 COR I I CH2 HC--C\ og c-o R 1 wherein R at each occurrence 1s a member independently selected from the group consisting of lower alkyl, hydrogen, and alkali metals.

2. A compound of the formula wherein n is an integer of 0 to 4. 3. A compound of the formula wherein X is a member selected from the group consisting of sodium and potassium.

4. Beta-(dicarboxymethyl)caprolactam.

5. A compound of the formula wherein R is a member selected from the group consisting of hydrogen and lower alkyl.

8 6. Beta-(carboxymethyl)caprolactam. 7. Beta-(carbethoxymethyl)caprolactam. 8. A process for the preparation of a compound of the formula (If-O (CHzMCI-I wherein n is an integer of O to 4, said process comprising reacting alpha, beta-unsaturated caprolactam with a sodium dialkyl malonate of the formula 2,708,194 5/1955 Blicke 260--239.3

4O HENRY R. JILES, Primary'Examiner. R. T. BOND, Assistant Examiner.

U.S. Cl. X.R. 260-78 

